Semantics, semantics everywhere !
Engine braking, basically you downshift and just dump the clutch (relatively), forcing the engine to catch up to the transmission. Which basically acts like a brake the time it gets to the correct revs. Hence the name. Brakes are strong enough now (and don't really fade much anymore) so that it's not used in modern racing. And drivetrain friction matters. I don't care if in theory it itself creates less force, if there's nothing connecting that friction to the driven wheels all you have then is tyre/wind/gravity. Hence why you have to be in gear to benefit from the effects.
And we're talking track driving. Sure, if you're at 7k there's a bit more friction slowing the car down than at 2-3k, but it's very slight and when you downshift on track you don't exactly go that low anyway. You don't have to redline it every downshifts, just go a gear at a time, no need to rush really (in H-Pattern cars you can even skip gears...). I don't get why people are so aggressive with their gearbox, it's so pointless.
I don't dump the clutch, I heel and toe mostly because it's fun, and to always be in gear as opposed to staying in neutral, which actually is better for fuel and helps slowing down a bit. But you also don't really want the revs to drop to idle territory, hence why the downshifts.